Protective effect of BCG vaccination in a nursery outbreak in 2009: time to reconsider the vaccination threshold?
- 1European Centre for Disease Prevention and Control (ECDC), Stockholm, Sweden and HPA Centre for Infections, London, UK
- 2HPA Centre for Infections, London, UK
- 3North West London Health Protection Unit, HPA, UK
- 4St Mary's Hospital, London, UK
- 5Chelsea and Westminster Hospital, London, UK
- 6TB Section, HPA Centre for Infections, London, UK
- 7School of Medicine, Health Policy and Practice, University of East Anglia, Norwich, UK
- Correspondence to Jaran Eriksen, Centre for Infections, Health Protection Agency, 61 Colindale Avenue, London N1 6JB, UK; jaran.eriksen{at}ki.se
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Contributors JYC, VM and BW collected the data during the outbreak. EA and SW assessed, diagnosed and treated the children during the outbreak. JE and IA designed the analysis protocol. JE, IA and JYC analysed the data. JE and IA wrote the paper. JE, IA, JYC, VM, BW, EA and SW interpreted the data. JE, IA, JYC, VM, BW, EA and SW critically reviewed all material. JE and IA are guarantors.
- Received 6 April 2010
- Accepted 16 September 2010
- Published Online First 28 October 2010
Abstract
Background In July 2008 a case of smear-positive pulmonary tuberculosis (TB) in a white UK-born nursery teacher was notified in London. The case had been symptomatic for 9 months while working in the nursery. The outbreak is described and the protective effect of BCG vaccination against latent Mycobacterium tuberculosis infection as measured by an interferon gamma release assay (IGRA) is assessed.
Methods Screening by chest X-ray and IGRA of nursery children, staff and their contacts was conducted using a ‘stone-in-the pond’ approach. Information was collected on various factors including BCG vaccination status, and data were analysed using multivariable logistic regression.
Results Overall, 168 children, 31 staff members and 57 other adults associated with the nursery were screened for TB. There were 12 cases of active TB and 43 cases of latent TB (72% children). 37.5% (95% CI 18% to 56%) and 40% (95% CI 30% to 50%) had a positive IGRA among teachers and children, respectively. 42% of children and 60% of adults were BCG vaccinated. In the adjusted analysis, BCG vaccination showed a significant protective effect against M tuberculosis infection in children (OR 0.25, 95% CI 0.09 to 0.69) and being taught by the index case was associated with acquiring TB infection (OR 18.91, 95% CI 4.43 to 80.79). A vaccine effectiveness of 66% was calculated, implying that 21 of the 32 infections could have been avoided if all children had been vaccinated with BCG.
Conclusions This outbreak shows extensive transmission of TB among very young children. BCG seems to have a protective effect against TB infection as assessed by positive IGRA in this cohort.
Footnotes
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Competing interests None.
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Ethics approval This study was carried out during an outbreak investigation. The Health Protection Agency has Patient Information Advisory Group approval to hold and analyse communicable disease data for public health purposes under Section 60 of the Health and Social Care Act 2001.
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Provenance and peer review Not commissioned; externally peer reviewed.
